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Since the design is the same, the difference should be traceable to a specific cause.","posed_since":"2024","precise":"The NIST measurement (2026, Metrologia), using a torsion-strip balance of the BIPM design in both servo and Cavendish modes, gives $G = 6.67387e-8\\,\\mathrm{cm}^3\\,\\mathrm{g}^{-1}\\,\\mathrm{s}^{-2}$, about 235 ppm below the BIPM 2013 value. Identify the effect (mass metrology, torsion-strip anelasticity, source-mass density inhomogeneity, alignment, environment) that accounts for the difference.","problem_ref":null,"references":"","settled_by":"A cross-check with exchanged source masses or fibers, or a third realization of the same apparatus, that isolates the component responsible for the 235 ppm offset.","status_note":"NIST's blinded result was unblinded in July 2024 and published in April 2026.","title":"Same apparatus design, different G: the NIST versus BIPM 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